TEFL is both a course and a certification. Short for Teaching English as a Foreign Language, the TEFL certification is a basic qualification to teach English to speakers of other languages. It can be used abroad or in an English-speaking country to teach newcomers. Don't confuse the TEFL with the TOEFL exam, which is required for entry into English-speaking colleges or universities when the applicant isn't fluent.
Be sure you understand the course outline and the course requirements. They are important to prepare you for what lies ahead.
Attend every class, be alert during instruction, take notes and read all the handouts you receive. Complete all the small assignments and all projects on time, and be prepared for quizzes.
Study a day ahead. If you read the next day's lesson from the material supplied to you, class instruction will seem like a review.
Build a solid relationship with your instructor. Don't hesitate to ask questions during class or ask for extra help during their office hours.
Form a small study group with other students. Hold regular meetings and practice the teaching techniques that you learn.
Know the needs of the students you plan to teach. It makes a big difference whether your audience will be students in Seoul or business professionals in Prague.
Get plenty of rest before any major TEFL exam. Feeling burned out is a big mistake that will reflect on your performance.